Voters are unimpressed and confused by the cryptic, stylised nature of many party political ads as the pre-election campaigning shifts into gear. The Tory poster featuring a woman crying a red tear and Labour's "Enough is Enough" poster in which "Tory Govt" is tattooed across two fists are just two ads criticised by voters in research published this week by the advertising agency Ammirati & Puris/Lintas.

Conservative supporters condemned the "red teardrop" poster for admitting that New Labour is different from Labour in the past. The colour scheme - red on monochrome - was disliked for too closely resembling traditional Labour imagery. The ad's concept was dismissed as illogical and misleading by Tory and Labour voters alike. The images of misery accurately depict how respondents feel now, but these feelings are associated with the present government, not with Labour, the findings show.

However, Labour's recent advertising did not escape censure. Only a minority of those surveyed recalled seeing the "Enough is Enough" campaign which includes a poster depicting two grabbing hands and the strapline "22 Tory tax rises since 1992". The tattooed fists in another ad were dismissed as "inappropriate". "That ad is common: it doesn't represent the Tories for me," one respondent observed.

Yet in spite of this, Labour's recent advertising came out ahead of the Tories', APL's study shows. Unlike many of the Conservatives' recent posters, Labour posters were acknowledged by both Tory and Labour voters as carrying clear messages underlined by a fact.

The agency, whose advertising clients include Birds Eye, Lever Brothers and Nestle Rowntree, conducted the research last week (14-15 January) among a cross-section of voters in Slough. All had switched political allegiance at the last election - half from Labour or Liberal Democrat to Conservative, half from Tory to Labour or Lib Dem.

"These so-called switchers are regarded as the key battleground by both the major parties," APL board planner Malcolm White explains. "Those switching to Conservative were slightly more positive about recent Tory ads such as 'teardrop', but even they were confused by its message. They may not have agreed with Labour's 'Enough is Enough' campaign, but at least they understood it."

All respondents criticised the emphasis on "negative advertising", particularly for the Tory posters which focused more on the possible future under Labour, less on hard facts. White adds: "Conservative voters were disappointed in their own campaign and found it difficult to defend. The Tories have successfully got a lot of attention but haven't got a lot of effective impact." This was underlined when voters were polled on past campaigns. Although all remembered last year's "demon eyes" ads, the majority remembered the ensuing uproar rather than the poster or message, "New Labour, new Danger".

The findings seem to fly in the face of advertising industry opinion. Earlier this month, Campaign magazine voted the "demon eyes" campaign, created by M&C Saatchi, campaign of the year. "Its success provided the Tories with one of the few bright spots in a disastrous year," the magazine enthused.

The Campaign jury might have a point. While APL's findings suggest a mature electorate tired of playground politics (respondents apparently desire information and facts instead of a one-dimensional, emotional approach in political ads), it is the simple negative that sticks in the mind longest. The best-remembered ad of recent years was the Conservatives' "Tax Bombshell" ad at the last election.

Labour can take heart, however, from the electorate's growing cynicism. Those surveyed by APL were deeply cynical about politicians' threats about what might happen if their party is not elected. "Back in 1992, looking into the unknown future was very frightening," says White. "This certainly doesn't seem to be so much the case today".